Paper

Two "working class," primarily Hispanic, elementary schools in Phoenix, Arizona, participated in the study. 245 schoolchildren aged 6 to 12 years received either a daily vitamin and mineral supplement at half of the U.S. RDA for 3 months or a placebo. 125 children given the supplements gained on average 2.5 IQ points over the 120 children given placebos. A significantly higher proportion of children in the supplement group gained 15 or more IQ points when compared to the placebo group. However, many children in the supplement group showed no more improvement than the placebo group. According to the researchers, this study confirms that vitamin-mineral supplementation modestly raised the nonverbal intelligence of some schoolchildren by 2 to 3 points but not that of most schoolchildren, presumably because the majority were already adequately nourished. They also suggest that there were greater improvements in some of the children because they may have been too poorly nourished before supplementation for optimal brain function.